As an enhancement to the release99/release4 (rel99/rel4) downlink shared channel (DSCH) concept in the third generation partnership project (3GPP) shown in FIG. 1(a) it has been agreed to add a so-called High Speed Downlink Packet Access (HSDPA) concept as a part of the 3GPP rel5 universal terrestrial radio access network (UTRAN) architecture as shown in FIG. 1(b). In FIG. 1(a) the DSCH is transmitted on a downlink Physical Downlink Shared CHannel (PDSCH) 10. In principle, the new HSDPA concept of FIG. 1(b) is an enhancement, because the leading idea in 3GPP has been to make HSDPA as an evolution from the shared channel concept not as a revolution. Therefore the defined solutions should resemble as much as possible the solutions which have already been defined for the shared channels. The basic idea behind the HSDPA is to offer a shared high speed channel with a higher data rate and a quick retransmission mechanism (i.e. with HARQ (=Hybrid Automatic Repeat Request)) from Node B. As can be seen by comparing FIG. 1(b) to FIG. 1(a), the Node B is given more intelligence for the purpose of handling retransmissions and scheduling functions, thus reducing the round trip delay between the mobile device and the RNC formerly handling retransmissions in FIG. 1(a). This makes retransmission combining feasible in the mobile device. In place of the variable spreading factor and fast power control used for the DSCH of FIG. 1(a), the HS-DSCH of FIG. 1(b) uses adaptive modulation and coding (AMC) in addition to the HARQ. A much smaller transmission time interval (TTI) of two milliseconds is also used instead of the 10 or 20 milliseconds of the DSCH. Also, the media access control (MAC) is located in the node B instead of the RNC. The AMC part of HSDPA utilizes adaptation of code rate, the modulation scheme, the number of multi-codes employed, as well as the transmit power per code. Even though many parameters are defined in the Radio Network Subsystem Application Part (RNSAP; see 3GPP TS25.423 v5.0.0) and Node B Application Part (NBAP; see 3GPP TS25.433 v5.0.0) to support HSDPA, the HSDPA discussion is on-going in 3GPP and many useful parameters are being added.
The user equipment is able to send a channel quality indicator (CQI) on the uplink HS-DPCCH (high speed dedicated physical control channel). It indicates the selected transport format resource combination (TFRC) and multi-code number currently supported by the UE.
FIG. 1(c) shows further details of the proposed UTRAN side overall MAC architecture including the new MAC-hs. MAC-hs provides the essential functionalities to support HSDPA. MAC-hs has the scheduling function as well as HARQ.
Currently in 3GPP, the SRNC is supposed to send the CQI Power Offset, ACK Power Offset and NACK Power Offset to the UE via RRC layer messages. FIG. 2 shows a radio interface protocol architecture for HSDPA. The Power Offsets will be defined as relative to the DPCCH pilot bit. Then the UE will use these Power Offsets as follows:
When an uplink HS-DPCCH is active, the relative power offset ΔHS-DPCCH between the DPCCH and the HS-DPCCH for each HS-DPCCH slot shall be set as follows:
For HS-DPCCH slots carrying HARQ Acknowledgement:
ΔHS-DPCCH=ΔACK if the corresponding HARQ Acknowledgement is equal to 1
ΔHS-DPCCH=ΔNACK if the corresponding HARQ Acknowledgement is equal to 0
For HS-DPCCH slots carrying CQI:
ΔHS-DPCCH=ΔCQI 
The values for ΔACK, ΔNACK and ΔCQI are set by higher layers (RRC message). The quantization of the power offset can be found in 3GPP TS 25.213 at Table 1A for instance.